a curved piece above the wheel of a bicycle or motorcycle to protect the rider from water or mud thrown up by the wheels | a wheeled vehicle that has two wheels and is moved by foot pedals |
| a single complete execution of a periodically repeated phenomenon |
| a periodically repeated sequence of events |
| a series of poems or songs on the same theme |
| an interval during which a recurring sequence of events occurs |
| the unit of frequency; one hertz has a periodic interval of one second (named for Heinrich Rudolph Hertz) |